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How to 'trick' PV into staying on during a grid outage

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  • #16
    Originally posted by SunEagle View Post
    While the SMA GTI has the ability to utilize up to 1500 watts of your pv array if the grid goes down the bad news is that without continuous sunshine even that power supply will fluctuate. That is why utilizing a battery system or generator is the only way to provide your loads a stable output.
    I already have a decent sized UPS for my home that powers my home office at full power for about 3 hours, more if I'm conservative. My thought was rather than an overly complex design with MB cutoffs and rewire the house at great cost, instead plug the SMA into the UPS which would then buffer the output, protecting electronics and providing stable power for my office needs versus trying to power the whole house which is unnecessary.

    For winter storm outages and/or night usage where PV output will be zero to little, switch back to the generator and let it do its thing.

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    • #17
      Originally posted by Burningislove View Post
      I already have a decent sized UPS for my home that powers my home office at full power for about 3 hours, more if I'm conservative. My thought was rather than an overly complex design with MB cutoffs and rewire the house at great cost, instead plug the SMA into the UPS which would then buffer the output, protecting electronics and providing stable power for my office needs versus trying to power the whole house which is unnecessary.

      For winter storm outages and/or night usage where PV output will be zero to little, switch back to the generator and let it do its thing.
      You're confused what the SMA SunnyBoy is. It is a grid tie inverter, just like you already have. You would need to replace your brand new inverter with the SMA SunnyBoy. When the grid is out, if it is sunny, you are able to throw a switch that allows one outlet to receive up to 1500W of AC directly from the solar panels. If the sun is down, no power. So yes, you could plug your existing UPS into that outlet, and the sun could charge your UPS to extend its use.

      What brand inverter do you have now?
      Solar Queen
      altE Store

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      • #18
        Originally posted by Amy@altE View Post
        You're confused what the SMA SunnyBoy is. It is a grid tie inverter, just like you already have. You would need to replace your brand new inverter with the SMA SunnyBoy. When the grid is out, if it is sunny, you are able to throw a switch that allows one outlet to receive up to 1500W of AC directly from the solar panels. If the sun is down, no power. So yes, you could plug your existing UPS into that outlet, and the sun could charge your UPS to extend its use.

        What brand inverter do you have now?
        Yes, I'm aware that my existing GTI (SolarEdge) would be replaced if/when I go forward. Since my SE is new, I'll likely wait until it's at EOL to replace it with something else (e.g. SMA), which is of course many years in the future I suspect (hope!). MA also has a rapid-shutdown requirement to meet legal code that must be considered. Many GTIs, including the one that my installer typically favors (favored), did not comply with this requirement and hence they switched to SE because it was one of the few that complies with code.

        I'd suspect the above MA code won't be an issue for many GTIs that don't currently comply, as I have many years before my SE fails and I'm sure many technologies will evolve during that time.

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        • #19
          SolarEdge is a fabulous product, expect a very long life from it. But if/when you do replace it, it's not as simple as switching it with a SMA. SolarEdge has the DC optimizers on the back of each panel, which is why it support rapid shutdown. They won't work without the inverter, so you'd have to remove all of them too. Much bigger project. DC coupling wouldn't work for you either for the same reason, the DC Optimizers need to talk to the inverter. Pretty much the only solution you'd have is to add AC Coupling, which is a bigger project as well.

          For the record, any grid tie inverter can comply with NEC 2014 Rapid Shutdown by using a disconnecting combiner box on the roof with a remote switch, like Midnite Solar's Disco Combiner and Birdhouse.
          Solar Queen
          altE Store

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          • #20
            Originally posted by Burningislove View Post
            Yes, I'm aware that my existing GTI (SolarEdge) would be replaced if/when I go forward. Since my SE is new, I'll likely wait until it's at EOL to replace it with something else (e.g. SMA), which is of course many years in the future I suspect (hope!). MA also has a rapid-shutdown requirement to meet legal code that must be considered. Many GTIs, including the one that my installer typically favors (favored), did not comply with this requirement and hence they switched to SE because it was one of the few that complies with code.

            I'd suspect the above MA code won't be an issue for many GTIs that don't currently comply, as I have many years before my SE fails and I'm sure many technologies will evolve during that time.
            your best bet is to wait for SolarEdge to announce the pricing on their upgrade of the inverter disconnect to support batteries and upgrade your solaredge inverter, wire up the office to the backup AC circuit and done.

            http://www.solaredge.us/files/pdfs/p...tasheet_na.pdf
            OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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            • #21
              Originally posted by ButchDeal View Post
              your best bet is to wait for SolarEdge to announce the pricing on their upgrade of the inverter disconnect to support batteries and upgrade your solaredge inverter, wire up the office to the backup AC circuit and done.

              http://www.solaredge.us/files/pdfs/p...tasheet_na.pdf
              Good idea. They are saying it will just be a firmware update to support the Tesla PowerWall 350V battery. I forgot about that.
              Solar Queen
              altE Store

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              • #22
                Originally posted by Amy@altE View Post
                Good idea. They are saying it will just be a firmware update to support the Tesla PowerWall 350V battery. I forgot about that.
                I think there is going to be some type of auto-transformer required for the PowerWall system.

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                • #23
                  Originally posted by SunEagle View Post
                  I think there is going to be some type of auto-transformer required for the PowerWall system.
                  you will have to replace the lower disconnect section below the inverter. For backup you will need an auto-transformer yes, and some re-wiring to get a backup breaker panel, and of course a battery of some kind.
                  OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                  Comment


                  • #24
                    No updates since 2015 but I think it will benefit the discussion. This new IQ8 micro-inverter from Enphase is probably the solution to all of the issues mention in this forum. Supposedly this new hardware will allow solar power to run a house without a power grid or batteries. We have to wait until 2019.

                    http://www.acsolarwarehouse.com/news...hout-the-grid/



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                    • #25
                      Interesting, But without additional storage to buffer the supply (clouds, etc.) and loads (refrigerator cycling on and off, etc.) this seems like a recipe for damaged equipment due to power transients. It might work in an off grid type application (without storage) for small pre-planned loads like lighting etc. which are more tolerant to unexpected outages. Presumably a smaller portable UPS could be fed by the IQ8 as well to act as a buffer.

                      But, I'm under the impression the Tesla AC powerwall can do this already today using a wide variety of existing inverters. Presumably other available/soon to be available AC battery systems (LG, Panasonic, Mercedes) could as well? Does anyone actually have one of these with an existing Enphase, SolarEdge, or string solution? Does it really work? Realistically, what's the total cost:
                      A) <$5K
                      B) $5K to $10K
                      C) $10K to $15K
                      D $>15K?

                      When I spit balled the two or three Tesla powerwalls I would need to cover my consumption and the necessary electrical work to install, I was looking at well over $15K. A very nice stationary generator can be had for the same price or less in many cases if natural gas or propane are available,

                      But I agree. There should be one central device which serves as both switch gear and storage into which multiple inputs can flow in (grid, solar, generator) and out (loads). That's what we do with commercial UPS systems that have multiple MAINS inputs (for grid and generator -- solar not so much).

                      It seems Panasonic and LG (in Japan and Korea) are already thinking along these lines. But their residential consumption needs are much less than in the US.

                      -Jonathan

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